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2011-02-06

Hard-tip, Soft-spring Lithography (HSL)

Researchers have figured out how to make designer nanostructures using arrays of silicon pens to create tiny patterns in biological and electronic materials. This is good news for researchers at least, as the method could make it cheaper to produce computer chips and gene chips for testing purposes, reports Technology Review.

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The technique is called hard-tip, soft-spring lithography (HSL). The technique basically uses hard pen tips that float on soft polymer springs. It’s different than the commonly used method called dip-pen lithography because HSL uses a hard tip instead of a soft pen tip.

The hard tip helps researchers make patterns with greater resolution. The print heads can be thrown away, giving this nanoprinting a disposable dimension to it.

Nanolithography is the branch of nanotechnology concerned with the study and application of fabricating nanometer-scale structures, meaning patterns with at least one lateral dimension between the size of an individual atom and approximately 100 nm. Nanolithography is used during the fabrication of leading-edge semiconductor integrated circuits (nanocircuitry) or nanoelectromechanical systems (NEMS).

Polymer Pen Lithography uses arrays of tiny pens made of polymers to print over large areas with nanoscopic through macroscopic resolution. By simply changing contact pressure (and the amount the pens deform), as well as the time of delivery, dots of various diameters can be produced. (The pen tips snap back to their original shape when the pressure is removed.)

Northwestern University researchers have developed a new technique for rapidly prototyping nanoscale devices and structures that is so inexpensive the “print head” can be thrown away when done.

Hard-tip, soft-spring lithography (HSL) rolls into one method the best of scanning-probe lithography -- high resolution -- and the best of polymer pen lithography -- low cost and easy implementation.

HSL could be used in the areas of electronics (electronic circuits), medical diagnostics (gene chips and arrays of biomolecules) and pharmaceuticals (arrays for screening drug candidates), among others.

To demonstrate the method’s capabilities, the researchers duplicated the pyramid on the U.S. one-dollar bill and the surrounding words approximately 19,000 times at 855 million dots per square inch. Each image consists of 6,982 dots. (They reproduced a bitmap representation of the pyramid, including the “Eye of Providence.”) This exercise highlights the sub-50-nanometer resolution and the scalability of the method.

Hard-tip, soft-spring lithography

[...] Here we describe a low-cost and scalable cantilever-free tip-based nanopatterning method that uses an array of hard silicon tips mounted onto an elastomeric backing. This method—which we term hard-tip, soft-spring lithography—overcomes the throughput problems of cantilever-based scanning probe systems and the resolution limits imposed by the use of elastomeric stamps and tips: it is capable of delivering materials or energy to a surface to create arbitrary patterns of features with sub-50-nm resolution over centimetre-scale areas. We argue that hard-tip, soft-spring lithography is a versatile nanolithography strategy that should be widely adopted by academic and industrial researchers for rapid prototyping applications.